Method for continuously manufacturing reinforced plastic board

ABSTRACT

Method for continuously manufacturing reinforced plastic boards and by a liquid resin impregnation step which comprises successively depositing a layer of a heat-hardenable synthetic resin and a layer of fibrous material onto a lower inert film, and maintaining the thus formed composite in intimate contact over an arcuate path by depressing the composite with a plurality of arcuately deposed filamentary members which contact the composite, depositing an upper inert film onto the composite, compressing the upper and the lower film-contained unit, whereby excess resin solution is intimately saturated into the fibrous mat. The filamentary members are removed from the compressed composite by the passage of the reinforced plastic board from the processing area. Apparatus for continuously manufacturing reinforced plastic board is also disclosed in the specification.

llnited States Patent I 1151 36mm Watanabe et al. 1451 Ar. W713;

[ METHOD FDR CONTINUOUSLY 2,771,387 11/1956 Kleist et al MANUFACTURINGREI 2,927,623 3/1960 Huisman et a]... PLASTIC BOARD 3,163,689 12/1964Ives 3,449,187 6/1969 Bobkowicz 156/1 78 [72] Inventors: ShigeoWatanabe; Tomomi Yamaguchi,

both of Fukushima-shi, Japan Primary Examiner-Carl D. QuarforthAssistant Examiner-E. E. Lehmann [73] Ass1gnee: Nltto Bosekl Co. Ltd.,Fukush1ma-sh1, Attorney sughrue,RothwelLMionzinn8Macpeak Japan 22 Filed;Nov. 8, 1968 ABSTRACT [21] Appl.No.: 774,279 1 Method for continuouslymanufacturing reinforced plastic boards and by a liquid resinimpregnation step which comprises successively depositing a layer of aheat-hardenable Foreign PP Priority Data synthetic resin and a layer offibrous material onto a lower Nov. 8 1967 Japan ..42/71442 mm, andmaintaining the thus frmed Composite in mate contact over an arcuatepath by depressing the com- 52 us. 01 ..l56/62.4, 156/179, 156/276,P08ite with a plurality of arcuately po ed fi amentary mem- 161/59 berswhich contact the composite depositing an upper inert [51] Int. Cl...B32b 17/04 film onto the composne compressmg h upper and the lower 58]Field of Search 156/178, 179, 181 300, 286, film'contained unit, wherebyexcess resin solution is intimatel56/62 4 161/59. 264/288. 56641 1ysaturated into the fibrous mat. The filamentary members are removed fromthe compressed composite by the passage 56] References Cited of thereinforced plastic board from the processing area. Ap-

paratus for continuously manufacturing reinforced plastic UNITED STATESP ATENTS board is also disclosed in the specification.

3,022,622 2/1962 Nolt ..56/34l 5 Claims, 1 Drawing Figure METHOD FORCONTINUOUSLY MANUFACTURING REINFORCED PLASTIC BOARD BACKGROUND OF THEINVENTION 1 Field of the Invention The present invention is related toan improvement in a resin solution-impregnation process, employed in thecontinuous manufacture of a reinforced plastic board, the process beingeffected by impregnating a fiber mat with a solution of a syntheticresin, and curing the same.

2. Description of the Prior Art In fiber-reinforced plastic boards,heat-setting resins, including polyester-epoxy resins as the syntheticresin, and reinforcing fibers, such as glass fibers, are often combined.The present invention is directed mainly to these combinations. However,the present invention can also be applied to instances where other typesof synthetic resins and reinforcement fibers are employed.

Methods for conducting the continuous manufacture of reinforced plasticboards of this kind usually comprises the steps of impregnating a fibermat with a solution of resin on a film, made of a material such ascellophane and synthetic resin. An inert film is placed on theimpregnated mat, the resultant assembly is passed through squeezingrollers to form the assembly into a flat board while squeezing outsurplus liquid and removing bubbles therefrom, and the board is thensubjected to a heat-setting operation.

It is a matter of importance in such an operation to insure completesaturation with the resin solution, without disarranging distribution ofthe fibers of the fiber mat. In addition, air located in the spacesbetween fibers and in the interior portions of the mat must becompletely exhausted therefrom. When a chopped strand mat of glassfibers is used, the failure of the resin to permeate into the spacesbetween the fibers located inside each strand will especially lead tothe occurrence of devitrification and internal patches. For this reason,there have been various proposals made with respect to procedures forapplying a resin solution, impregnation and squeezing techniques, and soforth, to solve the above problem.

The following problems have been encountered, in general: when a viscoussolution of resin was poured onto a fiber mat which was a mere scatteredaccumulation of fibers having no union therebetween, derangement of thedistributed fibers occurred; also, when the resin-impregnated mat wasfed to the squeezing rollers, the fiow of the solution squeezed out theresin caused displacement of fibers. For these reasons, the prior artproposed the following methods. One method comprised the steps of firstforming a uniform layer of a resin solution on a lower inert film,thereafter placing a fiber mat on the upper face thereof and thenapplying a pressure thereto to thereby eliminate bubbles and effectimpregnation. A second proposal comprised the steps of insertingadditional parallel filaments along the upper face of a fiber matalready impregnated with a resin solution to squeeze out the surplusliquid and to remove any bubbles while simultaneously preventing thedisplacement of fibers. These methods, however, were found to beinsufficient to insure retention of the distributed fibers, and also didnot allow complete evacuation of the bubbles.

Methods which are now practiced effectively on an industrial scale arerepresented by, for example, the method which is described in U.S. Pat.No. 2,927,623. This method comprises the steps of: forming a uniformlayer of a heat-setting resin solution on the upper face of lower inertfilm which is continuously transferred; placing on the surface of thelayer a single fiber mat of chopped strands of glass fibers; introducingalong the upper face of said layer while under tension in accordancewith the advancement of said mat, a number of parallel filaments alongan upwardly convexing path; forcing said filaments together with thefibers into the layer of the resin solution; supplying in a laminarfashion, an upper inert film onto the resulting face while passing theresulting laminar assembly through squeezing rollers to evacuate bubblestherefrom and to shape the assembly; and then subjecting the shapedmaterial to heat-setting. This method was ideal because saturation withthe resin solution could be accomplished without any derangement of thefibers. However, the introduced parallel filaments remained in theproduct, and causes a problem from the aspect of quality, including theexternal appearance and transparency of the product. In addition, theresidual filaments did not in any way contribute to the reinforcement ofthe product. Nevertheless, the inclusion of filaments was considered tobe unavoidable from the inherent requirements of this manufacturingprocess.

The present invention has succeeded, when a method such as that of U.S.Pat. No. 2,927,623 is practiced, in avoiding the retention of filamentsin the laminated product while preserving all beneficial effects of thisresin-impregnation method. The present invention is so conducted thatthe forcing of a fiber mat into the layer of the resin solution isperformed only during the step of impregnation with the resin solution.ln order to prevent the displacement of fibers which, may arise at thetime of squeezing the liquid, there have been provided filament threadsdisposed in parallel and extending in a stationary manner from a curvedpath along the face of the fiber mat passing through the squeezingrollers, the filament threads being maintained a proper distance fromthe nipping point of the squeeze rollers.

SUMMARY OF THE INVENTION The present invention provides an improvedmethod for continuously manufacturing reinforced plastic boards.

The method basically comprises depositing a layer of a heathardenablesynthetic resin onto a travelling lower inert film, and then depositinga layer of fibrous material onto the heathardenable synthetic resin. Thethus formed composite is maintained in intimate contact over an arcuatepath by a plurality of arcuately deposed filamentary members whichdepress the composite over the arcuate path. Prior to a compressionstep, where an excess resin is removed from the fibrous material, anupper inert film is applied onto the composite. The upper and lowerinert film-contained unit is then compressed, such as by squeezingrollers. The filamentary members are removed from the compressed upperand lower inert film-contained unit by the forward motion of thecomposite along the process treatment path. A lubricating effect of theresin solution and the spacing of the filamentary materials prevents anydisplacement of the fibers.

The composite is then, preferably, cured.

It is an object of the present invention to provide an improved processfor manufacturing reinforced plastic board.

It is a further object of the present invention to provide apparatususeful for manufacturing a reinforced plastic board.

It is yet another object of the present invention to provide a methodfor manufacturing plastic board wherein substantially no derangement offibers occurs and the reinforced plastic board does not containextraneous filamentary materials therein.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a side elevational viewof an apparatus for use in the process of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, numeral 1represents a lower inert film, such as cellophane, which is continuouslyfed from a reel 2. Numeral 3 represents a flat-faced table. Numeral 4represents a pipe for supplying a solution of a heat-setting syntheticresin such as a polyester resin containing a curing catalyst to theinert film. There is provided an arrangement such that the continuoussupply of this solution is effected at a predetermined rate by means ofa pump. Numeral 5 represents a doctor for uniformly distributing theresin solution, to a predetermined width, onto the face of the lowerinert film lying on the flat-faced table. Numeral 6 represents afibermat consisting of a uniformly distributed material, such as choppedstrands of glass fibers, this fiber mat being adapted to be disposed andcontinuously supplied onto a conveyor 7, a layer of a resin solutionpreferably being carried by conveyor 7. Numeral 9 represents, ingeneral, a number of idle rollers arranged so as to effect the transferof the lower inert film 1 along a curved path while in contact with therollers. Numeral 10 represents a roller provided at the forward end ofthe curved path for depressing the fiber mat 6, said roller beingrotated by being driven from a motor 11 in agreement with the velocityof the rollers provided adjacent the rear end of the curved path andadjusted so as to have a nipping clearance to produce a board of therequired thickness. Numeral 14 represents, in general, monofilamentthreads, such as synthetic fibers or steel wires, which have flat facesand which, like nylon for example, are not affected by the syntheticresin solution. Said threads are fixed, at one end, to a retainer shaft15, and passed around the lower periphery of said depressing roller 10and brought into contact with the upper face of the fiber mat lying onthe curved path. The threads are thereafter passed through the nippingclearance formed by the squeezing rollers 12 and 13. The other ends ofthe threads are located at a distance of about 30 50 cm. from thenipping point of the squeezing rollers 12 and 13 in the direction of theadvancement of said fiber mat. The threads 14 are disposed, in a largenumber, so as to form parallel rows and so as to be distributeduniformly over the width of the fiber mat. Normally, these individualparallel threads are spaced at about 10 mm. 40 mm. intervals. Aninterval less than 10 mm. is undesirable because of the occurrence offiber derangement due to friction between the fibers and the threads.Numeral 16 represents an upper inert film which is continuously fed froma reel 17 and is advanced, together with the lower inert film l and theresin-impregnated mat 6, through the nipping clearance formed by thesqueezing rollers 12 and 13. Numeral 18 represents a heat-treatmentfurnace for curing the resin by passing the resin-impregnated laminararticle therethrough, by means of a clip-tenter, or by any otherappropriate transfer means. Numeral 19 represents surplus resin solutionsqueezed out by the squeezing rollers 12 and 13, which is adapted to bereturned to a resin solution tank to be recycled after being removed,such as by a vacuum, and the like.

With this arrangement, the mono-filament threads 14 are retained in thestate of being sandwiched between the lower face of the upper inert filml6 and the upper face of the resinimpregnated fiber mat for a distancebeginning with the depressing roller 10 (the face of theresin-impregnated mat lying on the curved path) and ending at a siteabout 30 50 cm. from the nipping point of the squeezing rollers 12 and13 in the direction of the advancement of the mat so that the threadsare subjected to an intensive pulling force resulting from the movementsof these members, giving rise to a resultant depression of the fiber mat6 towards the face of the lower inert film 1 while the mat is beingpassed over the upwardly convexed path. The resin solution therebyeasily oozes out onto the upper face of the fiber mat 6, this effectinitially beginning at the site of depressing roller 10. The resinsolution which has been forced out exerts a lubricating action on themono-filament threads 14 which are brough into slidable contact with theupper face of the mat, so that they exhibit the function of effectivelydepressing the mat throughout the period in which the mat passes overthe curved path, hardly any displacement of the fibers of the matresulting. Thus, there will be given a sufficient time for the resinsolution to permeate into and saturate the spaces between the fiberswhile the upper face of the fiber mat is in its open state.

While the fiber mat 6 is being progressively covered under the upperinert film 16 by the squeezing rollers 12 and 13, the surplus resinsolution 19 which is contained in the mat will be forced out of the mat,together with the small amount of air still remaining therein, and thissolution flows on the upper face of the mat. However, the fibers of themat are still kept under the pressure of the mono-filament threads 14,and are not displaced. The fiber mat which has passed the nipping pointof the squeezing rollers 12 and 13 is not completely saturated with theresin and travels in its state of being in contact, under pressure, withthe upper and the lower inert films, and it thereby imparts an intensivesliding frictional force to the ends 14' of the stationary mono-filamentthreads, effectively preventing the tendency of the mono-filamentthreads 14 lying on the curved path of being displaced in the directionof the width of the mat. The length of the end portions 14' of thethreads from the nipping point of the squeezing rollers 12 and 13 isgenerally about 30 50 cm. to maintain the threads in their stabilizedparallel state, and this length is most preferable, although the exactlength could be varied by one skilled in the art in view of the presentspecification. A length less than 30 cm. may be applicable, but it isnot very effective for preventing displacement, and providing sufficienttension. While a length greater than 50 cm. may also be applicable, itprovides no increased effect, and there may occur troubles with the endportions of the threads being subjected to some harm from theheat-treatment furnace located in the subsequent stage so that the resinbecomes fixed on the end portions of the threads and causes derangementof the layer of the fibers. According to the manufacturing method of thepresent invention, there can be accomplished the impregnation andsaturation of a fiber mat with a resin solution almost ideally, withoutderanging the layer of fibers so that it is possible to obtain acontinuous fiber-reinforced plastic board.

Furthermore, in the above explanation, the invention was explained forthe case of employing a single resin liquid impregnating means and asingle heat-treatment furnace, but it will be understood that theinvention can be applied to a mass production system by positioning aplurality of resin liquid impregnating means in a vertical directionwith a suitable interval with respect to each other, and introducing aplurality of resin liquid-impregnated laminates from these means to asingle heat-treatment furnace.

What is claimed is:

1. A method for continuously manufacturing reinforced plastic boardutilizing resin impregnating solutions which comprises:

a. successively depositing a layer of a heat-hardenable synthetic resinand a layer of fibrous material onto a lower inert film;

b. maintaining said composite formed in the initial process step inintimate contact over an arcuate path by depressing the composite with apositively driven depressing roller and maintaining said composite in adepressed state with a plurality of arcuately deposed filamentarymembers, which contact the composite, said filamentary members beingspaced in a transverse distance from about 10 to about 40mm., apart;

c. depositing an upper inert film onto said composite;

d. compressing the upper and lower inert film-contained unit, whereby anexcess resin solution is intimately saturated into said fibrousmaterial; and

e. removing said filamentary members from the interior of said upper andlower inert film-contained composite,

said plurality of arcuately deposed filamentary members exerting a forceagainst the composite sufficient to urge the resin solution out and ontothe upper surface of the fiber mat, thus imparting a lubricating actionbetween said filamentary members and said fiber mat.

2. A method as in claim 1 wherein said filamentary members are fixed atone end thereof, and are removed from said upper and lower inertfilm-contained composite by the forward travel of said composite, theremaining end of said filamentary members being free.

3. A process as in claim 2 wherein said compression is performed bypassing said upper and lower inert film-contained composite throughsqueezing rollers.

4. A method as in claim 3 wherein the free end of said filamentarymembers extends from about 30 to about 50 cm. beyond said squeezingrollers.

5. A method as in claim 1 which comprises the additional step of curingsaid upper and lower inert film-contained composite. v

2. A method as in claim 1 wherein said filamentary members are fixed atone end thereof, and are removed from said upper and lower inertfilm-contained composite by the forward travel of said composite, theremaining end of said filamentary members being free.
 3. A process as inclaim 2 wherein said compression is performed by passing said upper andlower inert film-contained composite through squeezing rollers.
 4. Amethod as in claim 3 wherein the free end of said filamentary membersextends from about 30 to about 50 cm. beyond said squeezing rollers. 5.A method as in claim 1 which comprises the additional step of curingsaid upper and lower inert film-contained composite.